The use of saddle-type fuel tanks to increase fuel tank storage capacity in rear drive shaft vehicles is well known. The saddle-type fuel tank shape defines a first chamber and a second chamber for storing fuel. Typically, the fuel pump is located in the first chamber and fuel stored in the second chamber is transferred to the first chamber via a transfer pump. A first fuel level sender is configured to measure the fuel level in the first chamber, and a second fuel level sender is configured to measure the fuel level in the second chamber. A signal from each of the senders varies in proportion to the fuel level of the respective first or second chambers. A controller monitors the first and second fuel level sender signals in order to calculate the amount of fuel in the tank. If one of the fuel level senders malfunctions, the signal provided by the malfunctioning sender may not accurately represent the fuel level in the respective chamber causing the controller to calculate and provide an erroneous fuel amount to the engine control system and the instrument panel fuel gauge. An erroneous fuel amount indication may cause the engine control system to malfunction in regards to emission control. An erroneous fuel gauge reading may lead to a vehicle running out of fuel and stalling unexpectedly due to the vehicle operator being unaware of the need to refuel the vehicle. In addition, if the transfer pump fails and doesn't transfer fuel from the second chamber to the first chamber, the vehicle may stall unexpectedly due to the first chamber running out of fuel prematurely. Therefore, it is desirable to be able to diagnose these failures as soon as possible in order to provide adequate warning to the vehicle operator of a failed fuel system component and the corresponding need to service the vehicle.